The present invention relates to an automotive alternating current (AC) generator or alternator provided around a brush with a seal structure.
In an automotive AC generator or dynamo, it is necessary to provide a protective structure for preventing the invasion of water, oil or the like into a brush portion in which disposed are slip rings, brushes and a brush holder.
As a typical example of a conventional protective structure of this kind, as illustrated in the drawings of Japanese Utility Model Unexamined Publication No. 57-1077, there is a structure in which a semi-cylindrical slip ring cover is formed integrally with a rear frame of an alternator, and a brush holder is assembled with respect to the cover through a seal rubber.
In this typical structure, the seal rubber includes a seal portion for covering axial end faces of the slip ring cover and the brush holder and another seal portion to be inserted between the slip ring cover and the brush holder. These seal portions are formed integrally with each other as shown in, for example, the drawings of Japanese Utility Model Unexamined Publication No. 58-51663. In the assembling of this structure, the brush holder is positioned on the rear frame of the alternator with the seal portion of the seal rubber interposed between the brush holder and the slip ring cover. Subsequently, the other portion of the seal rubber is pressed in the axial direction of the alternator by fixing the rear cover for covering the brush portion and its neighborhood to the rear frame, thereby performing the seal of the brush portion in the radial and axial directions thereof.